[Rockhounds] RE: ID needed

[Mr EMan]

Dear Andri,
 Firstly for any and everyone: if you want an ID from a photo, please always include a general geographical location of where the sample was found AND in each photo place an commonly known object for scale. Having the location helps narrow probabilities when we are familiar with the geological and archaeological history of the find location.  These are nice sharply focused photos, Andri and are great to work with.

I have some candidate classes of objects so you can start looking for specific images/rock data. As you might have surmised by appearance I think the rock formed a skin of smoother crust as it cooled from a molten state.  This eliminates 99% of the worlds rocks from consideration.  It also has apparent melt veins and "vesicles" aka "gas bubbles". As to it being a natural "ore" of iron-- no I don't think so.  It may have high iron content but not necessarily native(metallic) iron. I'd like to know if a magnet sticks to any of it. (Probably not)

1. Slag from a smelting operation. Most Probable.  I have seen ditches lined with slag from a civil war era foundry which were subsequently filled-in so finding this at or below ground level isn't an exclusive clue. This is the most probable identification, IMO(in my opinion). I have also seen large boulders from a zinc smelting operation which are identical except for outside color. The glitter may be from "pot metal dregs" poured off with the rest of the slag. 

2. Clinkers/cinders from a furnace/smokestack similar to above but these usually aren't as large.  These and slag piles linger long after the evidence of buildings and other foundry artifacts have long gone. 

3. "Aa" Lava (also spelled aa, aʻa, ʻaʻa and a-aa: pronounced ah-ah) Depending on your location it could be lava but the bubbles and solid metalic sections tend to rule out lava. I mentioned lava because it often forms skins/crust over what is otherwise a rough surface and to see the difference between your rock and lava you may want to look at aa images.

4. Impactite: a very remote chance unless from a known astrobleme.

5. Mesosiderite meteorite: also a very low chance >.001% this is a meteorite. I mention it because a lot of folks jump to the conclusion of "meteorite" when they can't figure out what it is they do have. 

 I also mention these other rocks to illustrate the difficulty in making a positive identification solely based on photos. 

Hope this helps in your quest.
Eman


--- On Thu, 2/19/09, Andri <mustavidz at gmail.com> wrote:

> From: Andri <mustavidz at gmail.com>
> Subject: [Rockhounds] need help to identify these rocks
> To: rockhounds at lists.drizzle.com
> Date: Thursday, February 19, 2009, 4:52 AM
> Greetings to all the experts in the board!
> 
> I wish I could gather all detailed/technical info before
> posting this, but I'm not a geologist, so I dont know much about this
> specimen. I hope that is okay with the moderators. :) These rocks are taken as sample to what we believe is Fe (iron ore?), but the looks is abit unusual: black, shaped in chunks, weighing around 150gr,480gr, and 3kg for the biggest chunks. If you
 see the photos I attach here, you can see that the stones
 has some cavity (holes?) in it, and in some parts it glitters. These rocks were found in mountaineous location, and can be found both on the surface and beneath the ground.
 
> Please see photos here:
 
> http://img27.imageshack.us/img27/9241/480gr1du0.jpg (480gr)
> 
> http://img18.imageshack.us/img18/1807/150gr3dx8.jpg (150gr)
> 
> http://img22.imageshack.us/img22/1420/150gr2nh4.jpg (150gr)
> 
> http://img27.imageshack.us/img27/7719/3kgzd4.jpg (3kg)
 
 Thank you very much in advance,

> Andri